cross-posted from: https://discuss.tchncs.de/post/479621
Hi all! I defended my Ph.D. thesis back in 2019 and I also served as the creator and moderator for the subreddit r/FluidMechanics for a long time. I think with that I have gathered enough experience and courage to answer some of your queries. Some broad topics that I can answer questions on are:
- computation fluid mechanics
- scientific programming and HPC
- nonlinear shallow water equations
- statistical description of turbulence: spectra, energy budget etc.
- experimental methods: PIV
- stratified turbulence
- academia
- navigating your career pre- and post-Ph.D.
Ask away!
What is the difference between a solid and a fluid? Is it a discreet thing, or a spectrum?
I’m thinking of the pitch drop experience, and non-newtonian fluids.
It is a discreet thing if you consider pure materials. Phase transitions are sharp for all materials.
Non-newtonian fluids are usually a mixture of fine solid particles and liquid creating funky physics. Stress and shear rate are not linear as Newton’s law dictates. They can be shear thickening like corn starch in water or shear thining like blood. Shear thinning fluids are considered pseudo plastics, which is also a property in some solids.
I used to work with a guy with a doctorate in Hydrogeology. Is that the same thing? “It’s like geology, just add water…” was his description of his field.
Umm…no.
It is like physics but of liquids and gases.
To be precise study of motion and related phenomena in fluids. It used to be in the realm of classical physics. Then most physicists went over to relativity and quantum physics. So we engineers took over the subject.
Not sure if this is in your realm or not, but I’m working on a diversion tunnel for a dam and we’re installing orifice pieces of varying internal diameter to slow the flow rate of the water. The orifices are being installed in order from smallest diameter to largest which seems counterintuitive to me. I would think you would go in descending diameter size to slowly restrict the flow in steps. Could you shed any light on why this would be engineered this way?
Every orifice adds some drag into the flow, decreasing the flow rate. However if you would go for a descending size of orifices you would introduce a Venturi effect, increasing the velocity for a given flow rate. Think what happens when you squeeze the end of a gardening water hose; or what happens when you blow air out of your mouth.
